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Thursday, June 20, 2013

1743: The first mechanical ventilator

Stephen Hales (1677-1761)
(1, page 328)

Stephen Hales was among the great men of science who lived during the 17th century. Among other achievements, he was the first to accurately measure blood pressure, and invented an artificial ventilator used to purify air into prisons, ships, and granaries.

He was born in 1677 into the world of Isaac Newton, the man who inspired the scientific revolution. When Hales was only a boy of ten-years-old, Newton was at the peek of his career, publishing his book Philosophiæ Naturalis Principia Mathematica (Mathematical Principals of Natural Philosophy). It was in this book Newton published his laws of motion and laws of universal gravitation. Such wisdom, when he learned about it in school, must have inspired the young Hales. (4, page 66)

A young Hales would also have been influenced by Robert Boyle and John Mayow. Boyle's was a great chemist (some say alchemist) who was best known for his use of the scientific method and creating Boyle's law, which states the inverse relationship between absolute pressure the volume of gas. Mayow was such a great mind that, had he not died prematurely at the young age of 35, might have been the first to discover oxygen and carbon dioxide. (4, page 66-67)

As those great men set a path for men like Hales, he would do the same for those who followed in his tracks, such as Joseph Black, who discovered carbon dioxide, Joseph Priestly, who discovered oxygen, Scheele, who also discovered oxygen, Lavoisier, who also discovered oxygen and gave it a name, and Henry Cavendish, who discovered hydrogen.

Hales entered Corpus Christi College, Cambridge, in 1696, and studied science, botany, and chemistry. He was ordained in 1703, and he began his work on chemistry at the laboratory at Trinity College. In 1709 he was appointed as minister to the Parish of Teddington, where he would spend the rest of his life. He was married in 1719, although his wife died in 1721. lived died at the age of 83 in 1761. (4, page 65)(5)

His main contributions to science and physiology came in his Statical Essays that were published in two parts Vegetable Statics, published in 1727, and Haemastaticks, published in 1733.

In Vegetable Statics he discussed plant physiology and chemistry. Yet his most significant contributions to our history come from his later work Haemastaticks, which is described by britannica.com as the most significant contribution to the physiology of blood circulation since the works of William Harvey. (5)

In this book he described an experiment where he inserted into a blood vessel and allowed blood to rise up the tube. In this way he became the first person to accurately measure blood pressure. (5)

He also described measuring the capacity of the left ventricle of the heart, the output of the heart per minute, and the speed and resistance to flow of blood in the vessels. (5)

He became very interested in the spread of disease, and was aware that people in close quarters were more likely to catch diseases. Of course in his day, once you caught a disease such as tuberculosis, you were at the whim of God, meaning that there was little you could do but pray that you got better.

He knew that people who living in close quarters, in areas that were poorly ventilated, such as in prisons, ships, and granaries, were at an increased risk for becoming infected with diseases because they were all breathing the same stale air. Infections would easily spread from one person to another. (2, pages 241-243)

So he set out to invent something that could be installed at these places to ventilate air from the outside in order to freshen the air inside. What he ended up inventing was the first artificial mechanical ventilator which he introduced to the public in 1743.

He published his invention and opinions in his 1758 book "Treaties on Ventilators."

Sir John Simon wrote about "English Sanitary Institutions" in 1897, and explained how Stephen Hale's invention was also beneficial for people who spent time in prisons, military barracks, military hospitals, and aboard ships. He said:

Dr. Hales's "lungs"... seem to have been often advantageously used in ships, prisons and hospitals (the military was) ordered by the Lords of the Admiralty to adapt his "fire-pipes" to His Majesty's Navy 4 Readers of the present day who may find it hard to imagine the " putrid " quality of the atmospheres which in those days the inmates of prisons and ships and barracks and hospitals had to breathe, can well assist their imagination by referring to the pages of Hales and other contemporary reformers. (3, page 119)

John Pringle (1707-1782)
(1, page 374)

The invention was helped along by John Pringle, who who was a surgeon general of the British Army from 1742-1758, and considered the father of modern military medicine. (1, page 373)

He studied the spread of disease among the military, particularly fevers. He observed, along with others, that the more people were in a confined space, the greater likelihood the spread of fevers would be. (2, pages 241-3)

Attributing it to the stale air inhaled, he championed to have Hale's mechanical ventilators installed in hospital wards. (2, pages 241-3)

He discussed the importance of military sanitation, especially the importance of Hale's mechanical ventilator, in his 1752 book "Observations on the Diseases of the Army." He also wrote about the importance of antiseptics to prevent the spread of disease. (1, page 373)

The problem with the ventilator was electricity hadn't been invented yet, and so the machine had to be man powered. So, not only was the machine itself expensive, it was expensive to work and maintain. (1, pages 241-3)

So many military hospital wards resorted the difficult task of maintaining wards in well ventilated places such as "barns, churches, or ruinous houses. Of course the simplest and least expensive solution was simply to keep patients in the same poorly ventilated wards they were already in. (1, pages 241-3)

When this was the case, many such institutions worked hard to install as many windows as they could into such places. When new places were built, as many windows as possible were installed. Windows, therefore, were the least expensive option to improve ventilation, and by the late 1750s most hospitals had plenty of windows. (1, pages 241-3)(2, pages 241-243)

Of course, Pringle also said there was an increased effort to try to keep patients separated. This, along with better ventilation from open windows, seemed to help allay the problem, at least to a certain degree. (2, pages 241-3)

It got to the point that there are stories of patients who were lying sick in bed looking up through the holes in the ceiling at the stars and moon in the night sky, or feeling the hot sun upon their bodies during the day. This must have been a nice, refreshing atmosphere to get healthy in.

However, when the weather wasn't so friendly, such a venue must have posed a problem, especially when the rain or snow was falling.

To sum up the contributions of Hales I will quote Dr. Garrison:

Stephen Hales (was) an English clergyman of inventive genius, who enriched practical science in many ways, particularly as the originator of artificial ventilation." (1, page 328)